1. Field of the Invention
The present invention relates to an automatic photographic printing apparatus with a simulator and a method of adjusting the simulator, and more particularly, to a simulator which is capable of displaying on a CRT display an image which is to be printed on a photographic paper by an automatic photographic color printing apparatus, and an adjusting method therefor.
2. Description of the Prior Art
Automatic photographic color printing apparatuses have been known in which a negative color film is printed and then developed such that all of its print copies have the same photographic density and color balance irrespective of the density of the negative film (an underexposed, optimum-exposed or overexposed negative) by correcting the density using the integral transmission density (LATD) of the entire image in the negative color film and by performing the slope control thereon. Such an automatic photographic color printing apparatus generally comprises a light source, a light adjusting filter, a mirror box, a negative carrier, and an optical system having a black shutter, which are aligned in the apparatus in that order. In order to print a negative color film, the negative color film supported by the negative carrier is irradiated by the light source, and the black shutter is opened for a predetermined period of time (the exposure time is made constant) so that the image in the negative color film is formed on a sheet of photographic paper. The photographic paper on which the image of the color negative has been formed is then automatically developed by a developing process so that it becomes a print copy. In the automatic photographic printing apparatus of this type, the light transmitted through the negative is broken down into primary colors including red light (R), green light (G), and blue light (B) by the light receiving element. The density of each primary color is controlled using the LATD on the basis of Theorem of Evans, while the slopes of these three primary colors are controlled such that they have the same slope, so as to control the color balance. Thus, print copies prepared by this automatic photographic printing apparatus have the same density and color balance.
However, if the major subject in the color negative has the optimum density but the density of its background is higher or lower, this density of the background affects the exposure, resulting in density failure. The difference in color balance between the major subject and the background, e.g., the complementary relationship between the colors of the major subject and the background, produces color failure. In such a case, density compensation or slope control will not ensure a print copy of excellent quality, and the negative must be printed and developed again.
To obviate this problem, Japanese Patent Laid-Open No. 46731/1978 discloses a photographic inspection device provided with a simulator which is capable of displaying on a TV screen the image in a negative which is reproduced via a TV camera. In this device, the color video signals are adjusted such that the image displayed on the TV screen has a desired density and color balance, and these adjusted color video signals are employed to print the negative in an automatic photographic printing apparatus. Further, in the automatic photographic printing apparatus disclosed in the specification of Japanese Patent Publication No. 25220/1967, the image in a negative which is to be printed on the photographic paper is displayed on a TV screen, and the automatic exposure device is coupled to the resistor for adjusting the brightness and contrast of the TV. In either case, the image is simulated so as to reduce the frequency with which a reprinting and redeveloping process has to be resorted to.
However, in the method employing the photographic inspection device, the automatic photographic printing apparatus and the inspection device employ separate light sources. In consequence, even if the information obtained from the inspection device is employed to allow a print copy to be provided by the automatic photographic printing apparatus, the image formed on the photographic paper will not be the same as that displayed on the TV screen due to the use of different light sources and it is difficult to adjust both the light sources of the automatic photographic printing apparatus and the inspection apparatus to the same conditions and maintain the conditions.
Also, since the automatic photographic printing apparatus and the inspection device are independent from each other, after the exposure conditions in the former are determined the latter must be adjusted such that the exposure conditions in the latter coincides with those in the former. Such an adjustment requires much time and it is much difficult to conduct the adjustment accurately, resulting in a deterioration in simulating performance. Further, in a photographic printing apparatus in which the automatic exposure device is coupled to the resistor for adjusting the brightness and contrast of the TV, the TV signals are merely controlled such that an image displayed on the TV screen is appropriate even though the coloring characteristics of the TV are different from those of the photographic paper. Therefore, the image which is to be printed cannot be displayed on the TV screen.
The conventional TV has .gamma. of about 2.2, and this is corrected by providing a camera with a .gamma. correcting circuit which has .gamma.=0.45, by which the .gamma. of the entire apparatus to set to 1. On the other hand, the print copy tends to have a soft tone of .gamma.=2.0 so that it looks impressive, and it has therefore been necessary to provide a simulator with a .gamma. correcting circuit which corrects the .gamma. to 2.0 in correspondence with the .gamma. characteristics of the photographic paper. As a result, the .gamma. (about 0.6) of the negative is first decreased by the correcting circuit in the camera and is then increased by the .gamma. correcting circuit in the simulator. This leads to degradation of the SN ratio and to deterioration of the quality of the image on the TV. Further, two .gamma. correcting circuits are necessary, one in a camera and the other in a simulator, resulting in an increase in production costs.
In the case of printing an extremely underexposed or overexposed negative in an automatic photographic printing apparatus, the amount of light to be adjusted may exceed the adjustable range of the filter. In such a case, the exposure time is decreased or increased by means of a black shutter. When the exposure time is controlled by the black shutter, the intensity of light is not changed by the filter, and an image which is to be printed on a photographic paper cannot be displayed when the color negative film is imaged.
In a case where the exposure time is made to be very long, the length of exposure time is determined with the irregularity of reciprocity rule taken into consideration. This makes the image to be printed and to be displayed even more different from each other.
Furthermore, since the camera has a spectral sensitivity which differs from that of the photographic paper, the overlapping portions of the three primaries in the image reproduced via the camera are not exactly the same as those in the image printed on the photographic paper. Therefore, even after differences in the spectral sensitivities of the camera and the photographic paper have been electrically compensated for, color reproduction or color balance is deteriorated due to this difference in the overlapping portions. More specifically, photographic paper has a low sensitivity to red light, and, in order to compensate for this effect, the light from the light source has the spectral intensity characteristics shown by a curve H in FIG. 9, in which the intensity of red light is large. The base portion (the non-exposed portion) of the negative has the absorption characteristics shown by a curve I in FIG. 9, so it absorbs blue and green light to a larger extent. As a result, when the base portion of the negative is irradiated by the light source, the light transmitted through the base portion of the negative has the spectral intensity characteristics shown by a curve J in FIG. 9. The base portion of the negative in this state is grey when printed onto the photographic paper. However, the intensity of red light (of wavelengths of about 500 mn to 700 nm) is large, and the peak wavelength of this red light is about 680 nm. On the other hand, the imaging device (a single-board camera employing a mosaic filter) has a spectral sensitivity as shown by the spectral sensitivity curve in FIG. 10, in which red and green light, and green and blue light are mixed by a large extent, and the peak wavelength of the red light is about 600 nm. As a result, when the color negative irradiated by this light source is imaged by the imaging device and displayed on the simulator, the three primary colors are mixed to a large extent. The peak wavelength of the red light of the imaging device does not match that of the red light of the negative-light source system, reducing the quality of the color reproduction. Also, the intensity of the red light of the negative-light source system is large, and the output for the red light of the imaging device may be saturated, lowering the quality of the color balance.